Block Dissection Research Articles

Outcomes of Prophylactic Inguinal Lymph Node Dissection in Malignancies of Lower Limb.

To evaluate the role of early prophylactic inguinal node dissection in patients with squamous cell cancer and melanoma of lower limb. From 2008 to 2018, a Tertiary Care Hospital connected to a teaching institute served as the site of this retrospective observational study. Patient records were gathered with the purpose of gathering clinical, investigative, surgical, pathological and follow-up information. We included 33 patients in this analysis out of the 47 patients we treated ourselves between 2008 and 2018; among these 33 patients, 21 (63.63%) had palpable inguinal nodes at the time of primary presentation. All 21 patients' FNAC tests were positive for metastases, in 16 patients (76.19%). 5 patients on FNAC (23.80%) exhibited not metastases. The remaining 12 patients did not have enlarged lymph nodes at the time of their initial presentation. Patients who did not have palpable lymph node were given the option of having a modified inguinal block dissection. 8 patients with metastatic disease have nodes that are positive in histology. In addition, out of 5 patients with negative nodes 4 (80%) showed evidence of metastasis. The conclusion of this retrospective observational study is that although palpable lymph nodes in groin are unquestionably a sign that inguinal nodes should be dissected, prophylactic lymph node dissection should be still done even if nodes are not palpable or provide a negative FNAC result. Given that delayed lymphadenectomy has a significant effect on survival, delaying inguinal lymphadenectomy in non-palpable nodes could cause you to lose the battle against cancer in your lower limb. The related surgical morbidity is the only downside to prophylactic lymph node dissection. This can, however, be effectively decreased with a modified inguinal lymphadenectomy operation.

Nonmelanoma facial skin cancer: surgical planning for resection and reconstruction

Introduction The most effective treatment for nonmelanotic fascial skin cancer is surgical excision. Preoperative planning and a thorough grasp of reconstructive procedures, such as primary closure skin grafting, locoregional tissue flaps, remote tissue flaps, and free tissue transfer, are essential for the surgical therapy of these tumors. The choice of nonmelanoma skin cancer (NMSC) therapy is very specific to each patient and is influenced by the patient’s age, size, histologic subtype, and location of the disease. Treatment is to obliterate the lesion while maintaining normal tissue, function, and appearance. The ideas and methods of surgical excision and reconstruction of skin malignancies unique to the face were covered in this study. Patients and methods This study involved 98 patients of various ages and sexes. Of them, 89% had basal cell carcinoma and 11% had squamous cell carcinoma, both low-and high-risk tumors with varying sizes, locations, and histological subtypes. A safety margin of 3–5 mm is used for excision of low-risk malignancies and 5–10 mm for high-risk cancers. In 17 patients, skin grafts (split-thickness skin grafts and full-thickness skin grafts) are employed. 56 patients underwent local advancement, transposition, and rotational flaps; 15 patients underwent regional interpolation flaps; 6 patients sustained neck lymph node infiltration so they underwent cervical block dissection and distant pedicled flaps as latissimus dorsi muscle flaps; and 4 patients underwent cervical block dissection and free tissue transfer. Results Six patients experienced problems in the form of two partial graft and flap losses, two wound infections, and one scar retraction; however, with targeted care, they recovered well. Ninety-two percent of patients found the cosmetic outcomes satisfactory, and the functional outcome was good. Conclusion Wide excision and appropriate surgical reconstruction are ideal treatment modalities and may yield good aesthetic results or functional outcome, also the use of split-thickness skin grafts does not come as a first priority, where a lot of cases could have been treated with local flaps, as demonstrated in this consecutive series of treated patients. Treatment of NMSC on the face required a basic knowledge, presents a challenge to plastic surgeons, and is based on achieving the best oncological, functional, and cosmetic result. It is crucial to emphasize the need of patient education and appropriate tumor monitoring after NMSC therapy. A review of a big series of facial malignancy that may guide further studies cannot be understated.

Netuberkulózní mykobakteriální infekce v dětském věku

Introduction: Nontuberculous mycobacterial (NTM) infection of lymph nodes in young children is a rare disease. The increasing incidence has been observed after termination of vacciation in Czech Republic in November 2010. Aim of the study: To provide an overview of the clinical picture, dia gnostic options and therapeutic approach in children with neck lymph nodes aff ected by non-tuberculous mycobacteria. Methods: Retrospective cohort study of patients with confi rmed NTM infection treated at the Clinic of Otorhinolaryngology and Head and Neck Surgery of Faculty Hospital Hradec Kralove from 2010 to 2021. The inclusion criterion was proof of the causative agent of the disease (nontuberculous mycobacteria) by culture or molecular bio logical technique (PCR). Results: A total of 19 children with an average age of 26 months (range 12–42, SD 7.27) were enrolled. The most frequent pathogen was Mycobacterium avium (N = 16). Culture examination was positive in 84% (N = 16) of cases, PCR was positive in 47% of patients (N = 9). All children from the group underwent both surgical and antibio tic treatment. The most frequently used antibio tics were a combination of a macrolide antibio tic (clarithromycin) with an antituberculotic drug (rifampicin). In 6 children, an incision was made along with drainage of the lesion and for the duration of the infl ammation a complete extirpation of the pathological tissue under general anaesthesia followed. A total of 15 children underwent probatory extirpation of the pathological neck lymph node. We performed block dissections of the infected tissue in 7 children for residual infl ammation. Conclusion: The most eff ective treatment of the infection seems to be the exstirpation of all aff ected lymph nodes with surrounding tissue and combination of antibio tic (macrolide) with antituberculotic agent (rifampicin). Key words mycobacterial infection – nontuberculous mycobacteria – cervical lymphadenitis – children

Proof Without Words: A Pattern Block Dissection to Square the Regular Dodecagon

Summary This proof without words visually demonstrates that a regular dodecagon can bedissected into four congruent regular dodecagons using pattern blocks. Furthermore, a related result implies that it is feasible to square a regular dodecagon using pattern blocks.

Surgery for malignant melanoma - Expected standards

Melanoma surgery has changed significantly in recent years. The highly radical operations with many complications, in addition to which the complete and disease-free survival remained low, were gradually replaced by less radical operations. With the introduction of new systemic treatments (targeted and immuno-oncological) in adjuvant indications, certain surgeries, such as elective block dissections, have now been displaced from surgical treatments and the role of surgery has also been re-evaluated. The surgery for primary tumor removal, reexcision, sentinel lymph node biopsy and lymph region surgery, and surgical treatment of skin and distant metastases have changed. In this summary communication, the authors provide an overview of the currently accepted surgical therapy of melanoma malignum based on the international literature and their own practice.

O044 The risk of surgical site infection and other wound complications following surgery to the lymph nodes for staging or treatment of malignancy: a systematic review and meta-analysis of 45,415 cases

Abstract Introduction For completion of staging of malignant melanoma, sentinel lymph node biopsy (SLNB) may be offered to patients with stage 1B disease or greater, and in some positive cases, completion lymphadenectomy is offered. However, there is little evidence that either procedure are beneficial to patients, and both procedures carry a risk of wound complications. The aim of this study was to assess the current prevalence of wound complications in these procedures and quantify the change over time of this risk. Methods This was a subgroup analysis of a larger systematic review (Prospero CRD42021239530). A systematic search was undertaken to identify all published material relating to surgery on the lymph nodes. The primary outcome was the proportion of surgical site infection and/or seroma. Studies relating to malignant melanoma were selected from the overall results, and random effects meta-analysis of proportions and meta-regression were undertaken. Results Seventy studies were suitable for inclusion in meta-analysis, constituting 7,585 patients. The proportion of patients developing infection following SLNB was 3.5% (95% CI 2.0–6.0%) and seroma 7.8% (4.0–14.3%). For completion lymphadenectomy, the risk of SSI was 17.4% (13.4– 22.2%) and seroma 24.7% (23.4–26.0%). Neither SSI nor seroma incidence have changed significantly in 30 years. Conclusion The risk of complications in these procedures remains high and has not changed in 30 years. Given a potential lack of benefit of these procedures, this data should be used as part of the decision-making process when counselling patients, and to guide future research into prevention of wound complications. Take-home message The risk of SSI following block dissection for melanoma is almost 20%, and the risk of seroma almost 25%. This unacceptably high risk has not improved in the last 30 years.

New trends in the surgical treatment of axilla in breast cancer

Oncosurgical treatment of breast tumors involves the removal of metastatic axillary lymph nodes. In the last 30 years, the diagnosis and treatment of axillary lymph nodes have also undergone significant changes. The introduction of sentinel lymph node biopsy in 1993 made axillary block dissection with high morbidity safely omitted in a significant proportion of patients, and similarly, the staging of breast tumors and thus oncology and complex treatment became significantly more accurate. Shortly after the introduction of sentinel lymph node biopsy, intraoperative examination of sentinel lymph nodes (e.g. imprint cytology) also appeared, which significantly reduced the number of surgeries performed in the two sessions, thereby significantly reducing patient burden and surgical costs. The results of our study indicate that axillary block dissection is required in the treatment of axilla in an ever-decreasing group of patients and this proportion will decrease further in the future, with the increasing use of alternative axillary radiotherapy. The imprint cytological examination of sentinel lymph nodes taking into account current guidelines, no longer provides demonstrable benefits and its routine use is not justified. According to the latest international recommendations, intraoperative examination of the sentinel lymph node may be indicated in connection with mastectomy (when postoperative radiotherapy is not planned) and after neoadjuvant treatment. Our results suggest that the detection of suspected lymph nodes during preoperative axillary ultrasound may predict the stage of the disease. Based on our research results confirm that in patients receiving neoadjuvant therapy, in addition to the preoperative size of the tumour (≤20 mm,P= 0.002), the preoperative size of the lymph node (≤15 mm,P= 0.04) may also be used to predict that the stage of the disease is N0-1.

A human donor (cadaveric) observation study of three needle placements in the piriformis muscle

ABSTRACT Objective To compare the safety and accuracy of three dry needling locations in the piriformis muscle using human donors. Design Observational dissection study of embalmed human donors. Methods A licensed physical therapist of 17 years clinical experience and 5 years teaching dry needling placed three needles in a medial, midpoint, and lateral location of 14 piriformis muscles of seven embalmed human donors. Block dissection allowed for observation of tissues the needles traversed and recording of the structures that the needles pierced. Results The lateral needle pierced piriformis in 3/14 trials, and contacted sciatic nerve in 0/14 trials. The medial needle pierced both piriformis and sciatic nerve in 11/14 trials. The midpoint needle pierced the piriformis in 11/14 trials, and contacted sciatic nerve in 3/14 trials. Fisher’s Exact test (p < 0.001) found a nonrandom association between dry needle placement, and dry needle contact. Conclusions When dry needling the piriformis, a lateral approach can avoid the sciatic nerve, but cannot accurately pierce the piriformis tendon. Furthermore, while a midpoint and medial approach finds the piriformis muscle with the same accuracy, the midpoint location avoided the sciatic nerve more often.

Clipping inguinal lymphatics decreases lymphorrhoea after lymphadenectomy following cancer treatment: results from a randomized clinical trial

Background Post-operative lymphorrhea is a well-known complication of inguinal lymph node dissection. However, the interventions to reduce the duration of drain in situ have not been sufficiently elaborated. Objectives We evaluated the potential role of intra-operative mapping of lymphatic leakage with peri-incisional methylene blue injection and clipping of lymphatics after inguinal block dissection in reducing postoperative lymphorrhea. Methods We randomized 39 inguinal dissections done for various malignancies such as for carcinoma penis, urethra, malignant melanoma, rectum into 19 dissections (Interventional group) and 20 dissections (Control group). In the interventional group, after the completion of inguinal dissection, two ml of methylene blue dye was injected 4–8cm from the incision to identify the leaking lymphatics and they were clipped. Results The primary outcome was the decrease in duration of days of drain in situ and was found to have significant reduction of 3.07 days in the interventional arm. (p value-0.02). The secondary outcome was the reduction of 21 ml of mean drain output in the interventional group (p = 0.09). The number of lymphatics clipped was not found to have statistical correlation with the duration of drain in situ and the mean drain output. Conclusion The intraoperative mapping of lymphatic channels using methylene blue after inguinal dissection reduces the number of days of drain in situ.

Morbidity Following Groin Dissection in Malignancy Remains a Challenge: an Experience from North-East India.

Inguinal lymph nodal dissection is notoriously associated with high morbidity. Various risk factors and technical modifications have been described in the past to overcome complications like lymphedema, wound breakdown, and infection which adversely affect the postoperative outcome and quality of life of the patient. This is a retrospective observational study from 1 January 2016 to 31 December 2019 of patients who underwent inguinal/ilio-inguinal block dissection for malignancy. Lymphedema was the most frequent morbidity seen (24%). The mean hospital stay of patients following surgery was 9.7days (range 4 to 28days). The inguinal drain was removed on a mean of 17.7days (range 4 to 21days), while mean iliac drain removal time was 11.7days (range 4 to 21days).

Ultrasound-Guided Lateral Transversus Abdominis Plane (TAP) Block in Rabbits: A Cadaveric Study.

Simple SummarySmall rodents and, in particular, rabbits require special attention during anaesthesia since they develop a high level of stress following painful procedures or manipulations. The transversus abdominis plane (TAP) block is a locoregional technique that has been shown to provide good perioperative analgesia for abdominal surgery, reducing the stress during recovery from anaesthesia and the need for systemic analgesic drugs. The aim of this cadaveric study was to describe a US-guided lateral TAP block technique in rabbits and evaluate the spread of the dye administered by a single injection. Our results showed that this US-guided block is applicable and easy to perform in rabbits. However, a single injection of local anaesthetic may fail to cover the sensory component of the entire abdomen. It would be interesting to evaluate the same technique in vivo but using a double injection point, as recently described in other species.The aims of the study were to describe the ultrasonographic-guided lateral TAP block in rabbit cadavers and evaluate the spread of a lidocaine/methylene blue solution through a single fascial infiltration. The US-guided block and anatomical dissections were performed in 17 New Zealand rabbit cadavers. The probe was placed perpendicular to the column, one centimetre ventrally to the transverse processes, halfway between the iliac crest and the costal margin. External oblique (EO), internal oblique (IO), and transversus abdominis (TA) muscles were visualised, and 1 mL/kg of lidocaine 2% plus methylene blue 1% was injected. After dissection, the branches of spinal nerves stained were measured. Moreover, the percentage of length and height of the area marked were calculated. A good visualisation of the TAP was obtained in all 34 hemiabdomens. T11 nerve eminence was successfully stained in 52% of cases. T12, L1, and L2 were stained in 75%, 95%, and 100% of cases, respectively. L3 and L4 were stained in 60% and 40% of cases, respectively. The lateral TAP block with a single point of injection can be easily performed in rabbits, but it is not sufficient to cover the nerve eminences of the cranial abdomen. The two-point TAP block (lateral and subcostal) could represent a better option, particularly when large surgical incisions are required.

Study on treatment method of low efficiency well in S12 block

In recent years, the production decline of some oilfields is obvious, and a large number of oil wells begin to be in inefficient or ineffective production. Only by controlling these wells can the oilfields maintain effective production. By means of dynamic and static multidisciplinary integrated research, through elaborate dissection of typical potential blocks, the optimal treatment measures are selected from four aspects of “ reservoir heterogeneity and production status, type and distribution law of remaining oil, causes of low efficiency wells, classification and comprehensive treatment countermeasures and methods”, so as to provide technical support for potential tapping and comprehensive treatment of old oilfields.

Squamous cell carcinoma of tongue with isolated inguinal node metastasis: A case report and literature review

Most of the patients with squamous cell carcinoma of tongue present with distant metastasis to lung, bone, and liver. However, some rare presentation of tongue cancer metastasizing to cutaneous, cardiac, and axillary lymph nodes has been reported. We present a case of 55-year-old man diagnosed with squamous cell carcinoma of right lateral border of tongue, underwent right hemiglossectomy and right modified neck dissection, levels 1–5 with pathological staging pT2N0M0 (AJCC 8th edition) followed by adjuvant radiotherapy to a total dose of 60 Gy in 30 fractions. After 6-month post-treatment, the patient presented with right inguinal swelling which was associated with pain. Ultrasonography of the groin region confirmed lymphadenopathy and fine-needle aspiration cytology (FNAC) from lymph node came out as metastatic deposits of squamous cell carcinoma. Positron emission tomography and computed tomography (PET-CT) showed isolated right inguinal lymph node metastasis. He underwent right inguinal block dissection and adjuvant radiotherapy. Hence, isolated inguinal node metastasis is extremely rare but possible. Patient should be examined thoroughly during follow-up.

Combine preoperative estimation of serum thyroglobulin and ACR-thyroid imaging reporting and data system scoring could accurately define malignant thyroid nodules

Background: Evaluation of diagnostic ability of preoperative estimation of serum thyroglobulin (TG) to detect malignant thyroid nodules (TN) in comparison to the American College of Radiology, Thyroid imaging reporting and data system (ACR-TIRADS), fine needle aspiration cytology (FNAC) and intraoperative frozen section (IO-FS).Methods: 34 patients with ACR-TIRADS 2-4 TN were evaluated preoperatively for identification of malignancy and all underwent total thyroidectomy with bilateral neck block dissection if indicated. Results of preoperative investigations were statistically analyzed using the Receiver operating characteristics (ROC) curve analysis as predictors for malignancy in comparison to postoperative paraffin sections.Results: Preoperative serum TG levels had 100% sensitivity and negative predictive value, while ACR-TIRADS scoring had 100% specificity and positive predictive value with accuracy rates of 95.35% and 97.67% for TG and TIRADS, respectively. ROC curve analysis defined preoperative ACR-TIRADS class and serum TG as highly diagnostic than FNAC for defining malignancy with non-significant difference between areas under curve for TIRADS and TG. For cases had intermediate risk of malignancy on TIRADS, IO-FS had missed 3, FNAC missed 4, while serum TG levels were very high in the 13 cases and were defined by ROC curve as the only significant predictor for malignancy.Conclusions: Preoperative estimation of serum TG showed higher diagnostic validity than FNAC, high predictability of cancer and ability to verify the intermediate findings on TIRADS. Combined preoperative TIRADS and TG estimation could accurately discriminate malignant TN with high accuracy and spare the need for preoperative FNAC or IO-FS.

Pfannenstiel Scar Recurrences in Endometrial Cancers: A Case Series and Review of Literature

Endometrial cancer recurrences are usually either pelvic or distant metastases. Isolated scar recurrence is a rare entity, with approximately 43 cases being reported in the literature. The study highlights that most scar recurrences can be offered curative treatment with radical surgery. In our series, all the recurrences were in a previous Pfannenstiel incision scar. We report a series of four cases of isolated Pfannenstiel scar recurrences in patients with endometrial cancer who had undergone total abdominal hysterectomy and salpingo-oophorectomy. All four patients underwent curative radical surgery. Two patients had associated inguinal lymph node involvement, for which ilio-inguinal block dissection was done for one patient and en bloc resection of the node along with the recurrent disease was done for the other patient. We reviewed the previous literature to ascertain the possible aetiology of incisional recurrence, especially the isolated scar recurrences. In patients presumed to be having carcinoma endometrium, proper incision and surgical technique with good exposure, during the initial surgery, is important so as to minimise scar recurrence. Most of the isolated scar recurrences can be surgically resected with a curative intent.

V092 - Lateral approach to robot assisted inguinal block dissection for carcinoma penis

V092 - Lateral approach to robot assisted inguinal block dissection for carcinoma penis

USG-guided diagnostic block and hydro dissection for spinal accessory nerve entrapment syndrome

Spinal accessory nerve entrapment is difficult to diagnose due to its overlapping clinical features with other common diseases and nerve entrapments. It severely affects the life of an individual as normal neuronal physiology of the nerve is important for proper functioning and stability of the shoulder girdle. The patient develops symptoms like pain over the shoulder and neck, drooping of the shoulder, and weakness of overhead abduction of the arm. Ultrasound-guided block of this nerve has been described in the literature, but hydro-dissection using ultrasound as treatment has not been described yet. We have reported a case of spinal accessory nerve entrapment following sebaceous cyst excision in the posterior neck which was diagnosed clinically and confirmed using ultrasound-guided block and managed simultaneously by hydro-dissection. A case of 56 years female who underwent sebaceous cyst excision in the posterior triangle of the neck on the right side in May 2016. After 6 weeks of surgery, the patient developed pain in the right shoulder and gradually developed weakness in the overhead abduction of the arm. She went from one hospital to another for her pain relief but her pain remained undiagnosed and untreated. She came to Daradia Pain Hospital with complaint of pain in her right shoulder.

Performing Central Neck Dissection in Patients with Papillary Thyroid Carcinoma with Clinically Node Negative, Benefits and Drawbacks: A Comparative Study

Context: central neck dissection in addition to total thyroidectomy as a management procedure of patients with papillary carcinoma of the thyroid [PTC] was previously found to decrease the incidence of lymph node recurrence and allow and accurate PTC surgical staging that allow making a better decision regarding adjuvant radioactive iodine (RAI) ablation. But recently, central neck dissection in patients with clinical and radiological evidences of negative cervical lymph nodes was found to have many post-operative complications. Aim: to assess benefits, complications and drawbacks of performing central neck dissection by in PTC patients. Patients and methods: This is a prospective randomized study which included 70 PTC patients who was subjected to total thyroidectomy with or without neck dissection; all included patients have clinically negative cervical lymph nodes, 40 (60%) underwent total thyroidectomy in addition to central neck dissection and 30 (40%) patients were subjected to only total thyroidectomy without central neck dissection. We followed our patients for five years to detect recurrence, RFS and OS rates. Results: We found that operative time was longer in patients underwent central block dissection (p=0.049). Recurrence free survival and overall survival rates were not significantly different among both included groups, which denoted that central block neck dissection has no survival benefits in PTC patients. Conclusions: We have concluded that performing central neck dissection in PTC with clinically and radiologically negative lymph nodes has no benefits in increasing patients’ survival or decreasing recurrence rate and might lead to prolongation of operation time, increasing post-operative morbidity.

A PROSPECTIVE STUDY ABOUT THE SURGICAL MANAGEMENT OF THYROID CARCINOMA

INTRODUCTION : Thyroid cancer is one of the most common endocrine cancer and has the highest mortality among endocrine neoplasms. In India, its incidence is between 0.8–2 per 1,00,000 population. Early diagnosis and treatment remain the cornerstone of management to decrease the mortality rates. lack of prospective randomized trials, the management of these cancers generates tremendous controversy. study was planned to assess &amp; evaluate the management of various thyroid carcinomas. METHODS: A total of 40 patients were selected which were pathologically / histologically proven cases of Thyroid carcinoma in this Prospective study design in 2.5 years. Detailed Clinical Examination was done &amp; Prior to surgery all the patients went through investigations. Subjects included both the genders , all age groups including pediatric and geriatric age group and all classes of socio economic strata. RESULTS: No of female patients were 30 and male patients 10.Male :female ratio in this study was 1:3.FNAC / Biopsy / Cytology detected papillary carcinoma in 26 patients (65%) ,follicular neoplasm in 11 patients (27.5%) ,2 (5%) patients of anaplastic and one (2.5%) of medullary carcinoma. 86.6% of the patients had a firm gland &amp; hard gland and rest presented with a soft gland on palpation.Total Thyroidectomy with cervical block dissection was performed in 32 (80%) cases .Rest of the 20 % were dealt with Sub total Thyroidectomy with cervical block dissection. CONCLUSION: Most of the cancers present as a slow growing goiter for few months to few years duration.Most of the cancers are of papillary carcinoma type , FNAC detects the majority of the cancers and is an important diagnostic test.Thyroid cancers have a good prognosis as most of the patients present as Stage I disease &amp; most of the patients require total thyroidectomy with or without lymph node dissection followed by radio iodine ablation as treatment.Thyroid cancer,irrespective of the extent of disease,has good prognosis

Petrogenesis of ultramafic-mafic clasts in the Dos Hermanos Mélange, Ilocos Norte: Insights to the evolution of western Luzon, Philippines

The clasts of ophiolitic mélanges formed in orogenic margins reflect the tectonomagmatic history of a region and record the petrological signatures of oceanic lithospheres that interacted in the past. Exposed at the northwestern edge of Luzon, Philippines, the highly deformed Dos Hermanos Mélange (DHM) provides new insights on the complex history of western Luzon island. The DHM is a tectonic mélange composed predominantly of ultramafic-mafic clasts set in a sheared serpentinite matrix. The ultramafic clasts are mostly harzburgites with rare occurrences of lherzolite, dunite and chromitite. Petrographic (e.g. protogranular to equigranular texture) and geochemical characteristics (e.g. spinel Cr# = 0.17–0.60, olivine Fo content = 87–91) of the peridotites typify residual mantle peridotites which underwent low to moderately high degrees of partial melting. Mineral chemistry of some dunite and harzburgite samples (e.g. high spinel TiO2 = 0.01–0.64 wt%) further record subsequent modification of the depleted mantle material by arc-related processes (e.g. metasomatism). Most of the mafic clasts classify as gabbros and are composed of highly anorthitic plagioclase (An88–99) and Ti-poor pyroxenes which suggest derivation from arc-related melts. One troctolite clast, however, records the distinct petrographic (e.g. ophitic texture) and geochemical (e.g. low An content of plagioclase = 73–80) signatures of primitive MOR-related magma. These contrasting petrologic signatures in the ultramafic-mafic clasts of the DHM are similar to those observed in the crustal and mantle sections of the Eocene Zambales Ophiolite Complex (ZOC). This suggests that the DHM, like the ZOC, records the complex history of the convergence and emplacement of an ancient oceanic crust onto the Philippine Mobile Belt. Later tectonic processes in the region, which occurred after the emplacement of the ZOC, resulted to the extensive dissection and translation of ophiolitic blocks northwards transforming them into the DHM.